Metal (Mo, W, Ti) Carbide Catalysts: Synthesis and Application as Alternative Catalysts for Dry Reforming of Hydrocarbons—A Review

Abstract

Dry reforming of hydrocarbons (DRH) is a pro-environmental method for syngas production. It owes its pro-environmental character to the use of carbon dioxide, which is one of the main greenhouse gases. Currently used nickel catalysts on oxide supports suffer from rapid deactivation due to sintering of active metal particles or the deposition of carbon deposits blocking the flow of gases through the reaction tube. In this view, new alternative catalysts are highly sought after. Transition metal carbides (TMCs) can potentially replace traditional nickel catalysts due to their stability and activity in DR processes. The catalytic activity of carbides results from the synthesis-dependent structural properties of carbides. In this respect, this review presents the most important methods of titanium, molybdenum, and tungsten carbide synthesis and the influence of their properties on activity in catalyzing the reaction of methane with carbon dioxide.

Modification Strategies of Ni-Based Catalysts with Metal Oxides for Dry Reforming of Methane

“…In recent years, reviews on the catalysts for the DRM reaction mainly focus on specific metal or support materials, such as Ni-based catalysts [34], transition metal catalysts [35], Ni/Al 2 O 3 catalysts [36], silica-based catalysts [37], Lanthanoid-containing Ni-based catalysts [38], metal carbides [39] and alloy catalysts [40]. Very few works are focused on the applications of metal oxides in Ni-based catalysts relating to the modification impacts on the size, morphology, surface, and interface properties that are based on the catalytic activities and anti-deactivation behaviors in the DRM reaction; therefore, this review summarizes the state-of-art developments of Ni-based catalysts regarding the modification strategies (support confinement, metal-support interaction, oxygen defects, and surface acidity/basicity) of metal oxides (basic oxides, rare earth metal oxides, transition metal oxides, and mixed oxides) on the activity, selectivity, stability, and deactivation resistance in the DRM reaction.…”

Carbon Deposition Assisting the Enhancement of Catalytic Activity with Time-on-Stream in the Dehydrogenation of Isobutane over NiO/Al₂O₃

“…In other words, we suspected that carbon deposition, which is thought to be the main cause of catalyst deactivation, must have conversely contributed to improving the catalytic activity. Furthermore, it is o en highlighted that nanotube-like carbon deposition occurs around nickel catalyst (Helveg et al, 2004;Abdi et al, 2006;Czaplicka et al, 2021). However, there have been no such observations concerning metallic nickel species, which are the active species for this reaction.…”

Enhancement of the Catalytic Activity Associated with Carbon Deposition Formed on NiO/Al₂O₃ during the Dehydrogenation of Ethane and Propane

“…However, it should be noted that the main peak due to metallic Ni appeared at around 2θ= 44° in those gures, which matched the main peak due to Ni 3 C (nickel carbide) (Uhlig et al, 2013). Furthermore, similar carbide species are known to be active sites for the dehydrogenation of n-butane (Neylon et al, 1999;Kwon et al, 2000) and the dry reforming of methane (Czaplicka et al, 2021). Because the reaction temperature was relatively low for the formation of nickel carbide species (Czaplicka et al, 2021), it was assumed that metallic nickel was produced here.…”

“…Furthermore, similar carbide species are known to be active sites for the dehydrogenation of n-butane (Neylon et al, 1999;Kwon et al, 2000) and the dry reforming of methane (Czaplicka et al, 2021). Because the reaction temperature was relatively low for the formation of nickel carbide species (Czaplicka et al, 2021), it was assumed that metallic nickel was produced here. Based on the results shown in Figures 5 and 6, the formation of carbon deposition and the reduction of NiO to metallic Ni would improve yield of propylene as in the dehydrogenation of isobutane to isobutene on NiO/γ-Al 2 O 3 (Sugiyama et al, 2021).…”